Electric circuit interupter



Sept. 7,` 1937. E. a. MERRIAM I ELECTRIC CIRCUIT INTERRUPTER Filed Dec.24, 1934 1 l l l inventor y Ezra B. Merriam, b5 Nan/147 M/.4441

Hi' Attorrwe'g.

Patented Sept. 7, 19137 1 UNITED STATES ELECTRIC CIRCUIT INTERRUPTEREzra B. Merriam, Swarthmore, Pa., assigner to General Electric Company,a corporation of' New York Application December 24, 1934, Serial No.758,925

4 Claims.' (Cl. 20o-150) My invention relates to electric circuitinterrupters of the single pole type wherein the circuit 4is openedwithin a pressure chamber containing an arc extinguishing liquid such asoil, and the pressure generated bythe resulting arc is utilized to eiectexpulsion of liquid from said chamber for extinguishing the arc.

Electric circuit interrupters of the aforesaid typeare commonly known asexplosion chamber breakers and have long been used for interrupting highvoltage power circuits. A well known form of explosion chamber breakercomprises an insulated explosion pot forming the explosion chamberhaving at one end a xed contact structure. A coacting contact rod ismovable into said chamber through an exhaust opening or throat at theopposite end of said chamber. 'Ihe explosion pot and contact structureare immersed in a suitable insulating and arc-extinguishing liquid suchas oil, the oil filling the explosion chamber.

When the contacts are separated to open the circuit the Well knownexplosion chamber effect is obtained; that is, the pressure generatedwithin the explosion chamber by arc current causes a blast of oilthrough the arc as the movable contact passes through said throat. Thearc is generally interrupted at that point.

In modern electric power transmission systems operating at commercialfrequencies, it is highly desirable to limit the duration of arcing andhence the length of the arc. 'I'he conventional type of explosionchamber above described, however, utilizes the interrupting action ofthe blast mainly after the arc has been drawn throughout the length ofthe explosion chamber, i. e. at the throat. Although this results ineffective interruption of arcing operating requirements may necessitateeven faster interrupting time.

A principal object of my invention is the provision of an improvedsingle pole electric circuit interrupter of the explosion chamber type,as contrasted with an interrupter having two ormore breaks in the samechamber, which is simple and r,inexpensive in construction and which-iseffective to decrease the arcing time for breakers of the aforesaidtype.

In accordance with my invention in an operative form thereof, theexplosion pot or chamber is provided with an exhaust opening or portextending substantially transversely of the path of the arc, asdistinguished from the throat opening through which the movable contactmay operate. In this form, the width of the chamber corresponds roughlyto its length so that appreciable arcing spaceis involved. The arc maybe drawn eccentrically with respect to the longitudinal axis of thechamberI so as to be adjacent and transverse of said exhaust port, theremaining portion or' the explosion chamber serving as an oil reservoir.I have found that an explosion chamber breaker so constructed iseffective to interrupt the arc well within the explosion chamber so thatthe arcing time is limited to a few half cycles.

My invention will be more fully set forth in the following descriptionreferring to the accompanying drawing, and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims" annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is an eleval various single pole formsmy invention may asn sume.

Fig. 1 illustrates the circuit interrupting means i of one pole of anoil' circuit breaker comprising an explosion pot I, relatively movablecontacts 2 and 3, and an insulating and arc extinguishing liquid 4, suchas oil, in which the explosion pot and contact structure are immersed.It shall be understood that the term oil as used hereinafter is intendedto comprehend a suitable arcextinguishing liquid. The explosion pot l issuit-- ably formed o f a mechanically strong insulating material, suchas a laminated structure impregnated with a phenolic condensationproduct, and is secured in depending relation to a flange 5 of thestationary adapter 6. The lead-in conductor l is insulated with respectto the circuit breaker tank (not shown) by the usual high voltageinsulating bushing 8 at the lower end of` which,l at 9, is secured thecontact adapter.

'I'he fixed contact structure 2 comprises a butt contact resilientlybiased, as by a spring l0, to-

wards a lower limiting position into engagement with an annular arcingportion l I. The butt contact is electrically connected through flexibleconductors I 2 to the contact retaining structure i3 which iselectrically connected to the adapter 6 and hence to the leadinconductor l. l

At high voltages an insulating cylindrieai shield I4 is mounted on' aflange I5 which is supported. as at i6, by the explosion pot securingmeans.

The movable rod contact 3 is mounted at one end of a bridging member Il,the other end of which carries the contact of the other and similar poleof the breaker (not shown). The contact 3 is movable through an exhaustopening er throat I8 formed in the lower end of the explosion potopposite the iixed contact 2. As will be noted, the movable contactenters the explosion chamber eccentrically with respect to thelongitudinal axis of said chamber for coaction with the xed contact 2.

For the purpose of eiecting interruption of the circuit within theexplosion chamber and while the arc is still comparatively short, anexhaust port I9, which is restricted as compared with the volume of thechamber, is formed in a lateral wall of the explosion pot adjacent andopposite the path of the arc. As illustrated, the arc, generallyindicated at 20, is drawn transversely of the exhaust port I9 while thearc is comparatively short. I have found that with this arrangement thearcing time is appreciably reduced and that the arc is interruptedwellgwithin the chamber as compared with interruptions at or near thethroat I8.

One explanation of the improved interrupting characteristics of thisform of explosion chamber may be based on the fact that the arc, whichby reason of its Contact with the oil generates pressure within theexplosion chamber at a high rate, is subjected as indicated tothe washof the oil as it is expelled from the. chamber through the .lateral portI9.

In View of the fact that the throat I8 is still practically closed bythe movable contact 3, oil by reason of the arc pressurey within theexplosion chamber must exhaust at a high rate through the port I9 intothe exterior free oil body. The lines of flow converging toward the portI9 traverse the arc which is swept l toward the port and extinguished atthat point While the movable contact 3 is still within the explosionchamber.

. The eccentric positioning of the movable contact within the explosionchamber not only provides an appreciable oil storage space opposite theexhaust port in the event of heavy short circuits, but alsoadvantageously locates the arc with respect to the lateral exhaust portI9. In the event that the arc is not interrupted within the chamber theusual interrupting effect is also obtained at the throat I8.

In Fig. 2 the explosion pot I is fundamentally similar to that ofFig. 1. In this case the contact 3 moves centrally of the explosionchamber through the lower throat I8. The lateral port I9 is positionedin a side wall ofthe explosion pot as above described, andanllinsulating bailie 2I projects horizontally from the-inner wall ofthe explosion pot beneath the port: I9. The purpose of this balile is todirect the oil ilow from the explosion chamber so as to intensify thehow across the arc. The operation is generally similar to Fig. 1.

Fig. 3 illustrates a simple application of my invention to circuitinterrupters of the single break type wherein the movable contact memberis elevated to open circuit position. In this arrangement the circuitbreaker tank 22 is lled with oil to the level indicated,the tank havingsuitable insulating lining 23. A xed contact 24 is mounted at the lowerpart of the tank, and a movable rod contact 25 is guided for verticalreciprocal movement with respect to contact 24. The contacts coactwithin an interrupting chamber 26 formed by a strong insulating cylinder21 having a reinforcing lining 28. An insulating disk 29 forms the upperwall of the interrupting chamber. The rod contact 25 is guided within abushing 30 forming a throat at the upper Wall of the interruptingchamber.

For the purpose of obtaining the improved interrupting characteristicsabove described, the

' chamber 26 is provided with a lateral port at 3l substantiallyopposite the point of contact separation opening into the annular freespace 32 formed between the insulating cylinder 21 and the breakercasing. Accordingly, upon separation of the contacts 24 and 25 the arcpressure generated within the chamber 26 is effective to expel oil at ahigh rate through the port 3| for interrupting the arc at that point. Inthis arrangement Which is particularly adapted for comparatively lowvoltage power circuits, the arc is generally interrupted after a shortvertical travel of the contact 25 beyond the port so that there is nonecessity for moving said contact out of the interrupting chamber 26.

In Fig. 4 the explosion pot I 'is provided with the lateral port I9 at apoint appreciably beyond the initial formation of the arc. Asillustrated, the lateral port I9 is adjacent the throat I8 so that,although the arc length is increased, the oil flow across the arc isconcentrated at the'lower part of the chamber and is greatly intensifiedas the Contact 3 moves into the throat I8. A powerful cross blast effectis thereby obtained which has been found to be very eiective ininterrupting heavy short circuits. Y

In Fig. the explosion pot I is provided with an expulsion arc chute 33mounted within the lateral port I9 and arranged to form a channel forreceiving the arc. The expulsion chute 33 may be suitably formed ofplates of insulating material, the chute opening downwardly into the oilbody at 34. The chute preferably extends within the explosion chamber sothat the movable contact is drawn between the side-extensions of thechute. Accordingly, the arc drawn is within or at the entrance 33 ofthechute and is confined within the path of oil iiow as indicated so thatit is swept in a denite direction by the oil blast from the explosionchamber. It will be apparent, of course. that the expulsion chute mayexhaust directly outwards from the explosion chamber. Where, however,the breaker tank wall is close to the explosion chamber downward ventingof the expulsion chutevmay be preferred.

In the above-described arrangements for carrying my invention intoeffect, conventional contact structure is employed for interrupting thecircuit. However, other suitable circuit interrupting means may beemployed, the fundamental concept being that of forming a break anddrawing an arc within'an explosion chamber, or its equivalent,transversely of a lateral exhaust port through which oil from theexplosion chamber is expelled by the arc pressure at the aforesaid breakto cause interruption of the arc.

It should be understood that my invention is not limited to specificdetails of construction and arrangement hereof herein illustrata-i, andthat changes and modifications may `occur to one skilled in the artwithout departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A single pole electric circuit interrupter comprising an insulatingcasing forming a substantially undivided pressure confining chambercontaining oil, the width of said chamber corresponding approximately toits length, a xed contact disposed in said chamber and a coactingcontact movable in said chamber for opening the circuit at said fixedcontact, said casing having an exhaust port located adjacent to and atone side of the path of the arc drawn by said movable contact, the sizeof said arc chamber bearing such relation to said arc path andto saidexhaust port respectively that said arc is appreciably spaced fromthewalls of said casing, and the arc pressure generated Within saidcasing causes expulsion of oil at high velocity through said exhaustport for interrupting the arc at that point.

2. A single pole electric circuit interrupter comprising an insulatingpot forming a substantially undivided pressure conning chambercontaining oil, the width of said chamber corresponding approximately toits length, a xed contact disposed at one end of said chamber and acoacting rod contact movable along a path eccentric with respect to thelongitudinal axis oi' said pot for opening the circuit at said xedcontact, said pot having an exhaust port located adjacent andtransversely of said arc path, the size of said arc chamber bearing suchrelation to said arc path and to said exhaust port respectively thatsaid arc is appreciably spaced from the walls of said pot, and the arcpressure generated within said pot causes expulsion of oil at highvelocity through said exhaust port for interrupting the arc at thatpoint.

3. A single pole electric circuit interrupter comprising an insulatingpot forming a substantially undivided pressure confining chambercontaining oil, the width of said chamber corresponding approximately toits length, a xed contact disposed within said chamber and a coactingcontact movable ln said chamber for opening the circuit at said xedcontact, said pot having an exhaust port located substantiallytransversely of the path of movement of said movable contact adjacentthe point of initial separation of said contacts and initial formationof the arc, the size of said arc chamber bearing such relation to saidpath and to said exhaust port respectively that the arc is 'appreciablyspaced from the walls of said pot and the arc pressure generated withinsaid pot by said initial arcing causes, expulsion of oil at highvelocity through said exhaust port for interrupting the arc at thatpoint.

4. A single pole electric circuit interrupter comprising an insulatingpot forming a pressure confining chamber containing oil, a fixed contactdisposed in said chamber and a coacting contact movable through saidchamber for opening the circuit at said xed contact, said pot having anexhaust port located at one side of the path of the arc drawn by saidmovable contact, and means forming an arc chute in said chambercommunicating with said port including spaced insulating members betweenwhich said arc is drawn, the size of said arc chamber bearing suchrelation to said exhaust port that the arc pressure generated withinsaid pot causes expulsion of oil at high velocity through said chute andexhaust port for interrupting the arc within said chute.

' EZRA B. MERRIAM.

